The efficiency of a microscope depends primarily on the performance data and the correction quality of the microscope objective. For efficiency is affected by, for example, the aperture (resolution), the object field (the size of the intermediate image divided by the object magnification) as well as the spectral range for which the microscope objective is usable. The correction quality may usually be defined by data such as smoothing and color correction.
So far microscope objectives with apochromatic correction are only available for relatively small spectral regions, such as for example only for the visual spectrum, for spectral regions of ultraviolet to visible, or from visible to infrared. However, the newest microscopy techniques, in particular, fluorescent microscopy, require being able to work in the visible, ultraviolet and infrared wavelength ranges without having to change the microscope objective.
Such an objective is described in the U.S. Pat. No. 5,659,425, which is apochromatically corrected, however likewise only for a relatively small spectral region. In addition, the object field seizing with this objective is too small for many interesting applications due to the high object magnification.